Method of manufacturing electrical resistors



NOV. 22, 1966 c, GANCl 3,286,327

METHOD OF MANUFACTURING ELECTRICAL RESISTORS Filed July 27, 1962 INVENTOR. CHAQLIES. \l. GANG! Z44 r mp/vey United States Patent Ofitice 3,286,327 Patented Nov. 22, 1966 3,286,327 METHOD OF MANUFACTURING ELECTRICAL RESISTORS Charles J. Ganci, Bellerose Manor, N.Y., assignor to Ward Leonard Electric Co., Mount Vernon, N.Y., a corporation of New York Filed July 27, 1962, Ser. No. 212,914 Claims. (Cl. 29-15568) facture of such resistors by reducing the manipulative steps requiring hand operation.

Other and further objects and advantages will be apparent from the following description taken in connection with the drawings, in which FIG. 1 illustrates a plurality of uncoated resistors formed on a single core;

FIG. 2 is an enlarged view of two resistors with a vitreous enamel coating;

FIG. 3 illustrates the core of FIG. 1 mounted on a grinder to form the annular grooves;

FIG. 4 illustrates a ceramic cutting wheel for cutting the core into individual separate resistors; and

FIGS. 5 and 6 diagrammatically illustrate the attachment and forming of the resistance wire on the core.

The core 10 may be made of a ceramic or plastic material and have any desired length to accommodate a plurality of electrical resistors, such as resistors 11 to 14. In the case of a cylindrical core, it may be mounted in a centerless grinder with a core supporting roll 18 and a plurality of longitudinal grinding members 15 to 17 mounted on a shaft 22 for grinding the annular grooves 19, 20 and 21 in the core to divide the core into resistor bases 23, 24, 25 and 26 subsequently severed into separate resistors. The core is cleaned of dust particles and mounted in a wire winding lathe between centers 27 and 28. Instead of grinding the grooves 19, 20, 21, the grooves may be formed in the tubular member prior to the firing of the core. The metal or metal alloy terminals are than mounted in pairs 30, 31; 32, 33; 34, 35; and 36, 37 properly spaced on the bases 23, 24, 25 and 26, respectively, in any conventional manner. The formation of these grooves is optional and may be omitted. The purpose of the pre-grooving is to form rounded edges on the finished resistor.

The resistance wire 43 is supplied from the spool 44 through a guide 45 across the top of the core 10. The resistance wire 43 is welded to the terminals, as illustrated in connection with terminal 32 in FIGS. 5 and 6, or

otherwise fastened by winding on a projecting ear of the terminal and soldering. In the case of welding, the wire 43 is drawing across the top of the terminal with the terminal positioned between the electrodes 40 and 41. The electrodes may be mounted and operated in any convenient and conventional manner during the welding operation so that the electrode 40 moves down to engage the resistance wire 43, while the electrode 41 moves up to engage the terminal 32. The wire 43 is then welded to the terminal 32 and the electrodes 40 and 41 are retracted from the resistor. After the welding step the electrodes are moved so as to clear the tab of the rotating terminals.

As illustrated in connection with the resistor 11, after the resistance wire 43 is secured to the lead terminal the core is rotated to wind the resistance wire on the respective core, and at the end of the winding the resistance wire is drawn across the trailing terminal and spot welded as described in connection with terminal 32.

Thus the resistors 11 to 14 may be successively formed on the single core 10 without the removal of the core from the winding machine.

After all of the resistors are formed on the bases, the resistors as a unit on the core 10 go through the various finishing operations, such as cementing, inorganic or organic painting, vitreous enameling, terminal cleaning, tinning resistance measurement, marking and the like. Thus as illustrated in FIG. 2 the resistors will have an enamel coating 50 with grooves 19a, 20a, 21a formed in the coating between the resistors. After the resistors are completed, the core 10 with the resistors is fixedly mounted in a cutting machine having diamond abrasive or grinding wheels 46 to 48 for each groove 19a, 20a, 21a. The grinding Wheels have grinding edges 46a through 48a to sever the tubular core 10 into individual resistors by passing through the core and are cooled with water. Other cutting means may be used, such as hot electrical wire cutters.

In the preferred embodiment of the invention grooves 19a, 20a, 21a are formed in the core. However, the grooves may be omitted and the resistors formed in a similar manner and severed as described in connection with the preferred embodiment.

A vitreous enamel coating has been illustrated and described. However, other types of coatings may be used, such as organic, silicone, Teflon, silicate cements, hydrosilicate cements, phosphate cements, oxychloride cements, or the like. Also, silicone cements, Teflon bonded cements or the like may be used.

The advantage of this structure and method of manufacture is the easy handling of a plurality of resistors by the manipulation of a single core. Thus in the winding of the resistive elements the core is passed along as the resistive elements are wound thereon and secured to the respective terminals. There are no additional movements required in setting each individual resistor down and picking up the next, and in the operations such as resistance measurement, cementing, inorganic or organic painting, enameling, terminal cleaning, tinning resistance measurement, etc. By having a plurality of resistors on one core it is possible to reduce the number of manipulative movements for these various operations and reduce the cost of manufacture of the resistors.

I claim:

1. A method .of manufacture of electrical resistors comprising forming a straight core, fastening a number of terminals at longitudinally predetermined spaced intervals on said core and longitudinally arranged in pairs, said core having a clear portion between pairs, mounting resistive wire elements around said core between respective pairs of terminals and attaching and terminating said elements thereto to form a plurality of longitudinally spaced resistors with said clear portions therebetween, forming a solid insulating protective coating on said core to cover said resistive Wire elements and severing said core between the terminals of adjacent resistors to form individually separate resistors.

2. A method of manufacture of electrical resistors comprising forming a straight core having an outer surface, forming grooves around said core in said outer surface and longitudinally spaced along the core to define subsequently severed bases, fastening longitudinally arranged pairs of terminals on said bases between said grooves, mounting resistive wire elements between pairs of terminals and attaching and terminating said elements thereto to form a plurality of longitudinally spaced resistors, forming a solid insulating protective coating on said core to cover said resistive wire elements and forming inwardly rounded contours at the respective annular grooves to provide the finished core with rounded edges, and severing said core into individual resistors by grinding means passing through said core at said grooves.

3. A method as set forth in claim 2 wherein in the step of forming said core ceramic materials are used, and in the step of forming said coating applying a vitreous enamel frit and firing said frit to form a vitreous enamel coating.

4. A method as set forth in claim 2 wherein said core is made of a solid organic material.

5. A method as set forth in claim 2 wherein said coating comprises a cement.

References Cited by the Examiner UNITED STATES PATENTS 1,904,487 4/1933 Lyon .611 al. 29--155.62 2,247,869 7/1941 Beers 29155.68 2,596,325 5/1952 Cerny 29-155.68 2,628,300 2/1953 Berkelhamer 29-1557 2,887,558 5/1959 Tally- 29155.69 2,972,726 2/1961 Boykin 29-155.68 2,976,509 3/1961 McFaddan 29-155.69 x 10 3,078,550 2/1963 Rakowski 29 155.63

FOREIGN PATENTS 11,993 5/1914- Great Britain.

15 JOHN F. CAMPBELL, Primary Examiner.

CHARLIE T. MOON, Examiner.

J. W. BOCK, I. M. ROMAN CHIK, Assistant Examiners. 

1. A METHOD OF MANUFACTURE OF ELECTRICAL RESISTORS COMPRISING FORMING A STRAIGHT CORE, FASTENING NUMBER OF TERMINALS AT LONGITUDINALLY PREDETERMINED SPACED INTERVALS ON SAID CORE AND LONGITUDINALLY ARRANGED IN PAIRS, SAID CORE HAVING A CLEAR PORTION BETWEEN PAIRS, MOUNTING RESISTIVE WIRE ELEMENTS AROUND SAID CORE BETWEEN RESPECTIVE PAIRS OF TERMINALS AND ATTACHING AND TERMINATING SAID ELEMENTS THERETO TO FORM A PLURALITY OF LONGITUDINALLY SPACED RESISTORS WITH SAID CLEAR PORTIONS THEREBETWEEN FORMING A SOLID INSULATING PROTECTIVE COATING ON SAID CORE TO COVER SAID RESISTIVE WIRE ELEMENTS AND SEVERING SAID CORE BETWEEN THE TERMINALS OF ADJACENT RESISTORS TO FORM INDIVIDUALLY SEPARATE RESISTORS. 